Fix text change detection in IE

Introduce textchange event that get triggered when something changed
on input fields.

Refactor translation textarea construction. Set the value before
starting listening to events. Listen events only with one listener.
Set the two dirty flags together for consistency.

This eliminates the "You have unchanged saves" popup appearing in IE
even when there were no changes.

This fixes the case when it was impossible to get rid of unsaved
status for messages which have no existing status.

Bug: 47019
Bug: 46266
Change-Id: Ib5a7fecdf3cc42c7f5463bb03cae2326e1a3afbc